The kidney plays a crucial role in maintaining salt balance by two opposing physiological mechanisms: the renal dopaminergic system which enhances salt excretion and the renin-angiotensin system (RAS) which causes salt retention. Salt-sensitive hypertension occurs when this balance is altered or abnormal. We hypothesized that this balance is influenced by salt intake: therefore dietary salt affects the natriuretic response to the renal dopaminergic agonist Fenoldopam, and the Angiotensin Converting Enzyme inhibitor, Enalapril. In this trial we study normal salt balance mechanisms in salt resistant adults with normal blood pressure.
Eight adults of both genders and all races were studied in this double blind placebo controlled cross over study with randomization of the order of interventions. After 5 days each on low salt (about 1 gram/day) and high salt (about 6 grams/day)diet, with a washout period of at least four weeks in between, every subject was treated with Enalapril and Placebo on two consecutive days, followed by a Fenoldopam infusion for three hours, during which natriuresis and renal function testing were performed.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Masking
QUADRUPLE
Enrollment
45
Intravenous infusion at 0.5 mics/Kg/min for three hours
Georgetown University Medical Center
Washington D.C., District of Columbia, United States
Urinary sodium excretion
All subjects received placebo/enalapril in a randomized counterbalanced fashion in both phases. Phase 1 was on low salt, while Phase 2 was on high salt. All subjects received a 3 hour fenoldopam infusion, during which time urinary sodium excretion was measured as the primary outcome bvariable.
Time frame: During the trial: a 3 hour fenoldopam infusion
Renal Plasma Flow
In order to explain physiologically the effects of fenoldopam on urinary sodium excretion on high and low salt diet, with and wothout enalapril, renal plasma flow was measured during the infusion using PAH clearance
Time frame: During 3 hour fenoldopam infusion
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